Using lock nut adhesive for weak threads

Honest John Back Room » Technical matters
View Threaded
Thu 30 Oct 2003 13:43
Using lock nut adhesive for weak threads - andrew4
I have VW Golf Mk2 1.3.

The alternator pulley is connected to the crankshaft sprocket by four hex bolts. After replacing the timing belt, i.e. removing the pulley I now have 2 threads that are weak. When the bolts are inserted they hold little torque.

If I used lock nut adhesive on the threads and washers will this hold the bolts in place with a resonable torque?

What is the best lock nut adhesive for this? Will I be able to undo the bolts again if required in the future?


Reply | Report as offensive | Link
Thu 30 Oct 2003 13:54
Using lock nut adhesive for weak threads - Malcolm_L
I take it the threads have stripped on the crankshaft sprocket?

If 2 threads are now weak, then using loctite or any other adhesive will not significantly improve the torque settings.

Did you use a torque wrench or had someone else already over-torqued the bolts?
Reply | Report as offensive | Link
Thu 30 Oct 2003 14:36
Using lock nut adhesive for weak threads - martint123
Locktite and the like prevent the bolt from turning, not from pulling out. Your threads are damaged. I guess it's an aluminium pulley that they screw into?. Either replace it or insert Helicoil thread replacements - depends on the access if you can do it in place though. They work well in most situations.
Reply | Report as offensive | Link
Thu 30 Oct 2003 22:04
Using lock nut adhesive for weak threads - Dizzy {P}
Andrew,

The first thing to mention is that the threadlocking compounds commonly called Loctite are not 'adhesives'. Loctite doesn't penetrate or bond with the surface of the components, it works by filling the gaps and then hardening to give a mechanical lock.

Threadlocking compound has strength only in compression so putting it on the washers will do no good at all. These compounds can help secure components with worn threads but I would hesitate relying on this with a vital assembly like an alternator drive unless I was confident that the bolts, not the Loctite, are doing the holding. Loctite threadlocking compound is a plastic and is intended only to prevent loosening by vibration.

If you *do* go ahead, using Loctite Nutlock or Studlock would allow the bolts to be removed with normal hand tools in the future. I wouldn't rely on Screwlock as this would very likely be too weak to do much good at all in your situation. Various stronger Loctite's are available (numbered in the 6-- range unless they've changed in recent years) but these aren't really for threads because (a) they don't have such a good gapfill and (b) for removal they would require heating to about 200C, 300C for the strongest, in order to soften enough for component removal.
Reply | Report as offensive | Link

Real MPG enables you to register the fuel economy you are actually getting against your make and model of car, its engine and type of transmission.

Every time you enter an average consumption figure against your car, the overall average automatically adjusts to reflect it.

Real MPG